Investigations concerning the oxidation of arachidonic acid by prostaglandin synthase, lipoxygenases and possibly cytochrome P-450, and the relationship of this metabolism to regulation or modulation of biological processes. Arachidonic acid metabolism is studied in isolated cells, tissues or explants, where both the arachidonic acid oxidation and the biological event can be measured. Since the profile of arachidonic acid metabolism varies among different cells and tissues, characterization of the metabolites is an important part of the studies. We have investigated arachidonic acid metabolism in canine tracheal epithelial cells and showed that the formation of PGD2 correlates with C1- secretion. Factors that control or regulate arachidonic acid metabolism are also studied. Prostaglandin hydroperoxidase and peroxides play a role in regulation of PG biosynthesis. Other studies on arachidonic acid metabolism in cells were done primarily for future cooxidation studies. A major effort now, and in the near future, is an investigation of the possible role of arachidonic acid metabolism in mitogenesis.